Effect of BCL-2 on Harringtonine-induced apoptosis and intracellular Ca2+ mobilization in human leukemia HL-60 cells

Harringtonine (HT), a kind of anticancer drug isolated from Chinese herb Cephalotaxus hainanensis Li, has been used in the clinical treatment of human glanulocytic leukemia and chromic myelocytic leukemia. In this study, we investigated the effect of Bcl-2 on HT-induced apoptosis and Ca²⁺ mobilization in human leukemia HL-60 cells. 1 g/ml HT induced the apoptosis of HL-60/Neo cells in a time-dependent manner; while 1 g/ml HT failed to induce the apoptosis of HL-60/ Bcl-2 cells. HT-, A23187- (a Ca²⁺ ionophore), Carbonyl cyanide m-chlorophenylhydrazone (CCCP,a specific releaser of Ca²⁺ from mitochondria) and thapsigargin- (an inhibitor of endoplasmic reticulum Ca^2+> -ATPase) induced changes in Ca²⁺]_i were monitored by using Fluo 3-AM with confocal laser scanning microscopy. The results demonstrated that HL-60 cells with enforced expression of Bcl-2 (HL-60/Bcl-2 cells) had increased Ca²⁺ permeability and increased intracellular Ca²⁺ store in comparison with HL-60 cells with negative control vectors (HL-60/Neo cells), suggesting that Bcl-2 might prevent HT-induced apoptosis by increased Ca²⁺ permeability and increased intracellular Ca²⁺ buffering capacity.